The Killing Joke has always been one of the most iconic Batman stories of all time (and possibly the definitive Joker story), but the film adaptation had an extremely difficult time getting off the ground. It was in development hell for years before it recently started to move forward, and according to a new Empire interview with director Bruce Timm, the third time was the charm:

This is actually the third time that The Killing Joke came up for production. The first time, it was because we had told the home video department that chances are if we do this story, it's going to get an R rating... But right around the time we were ramping up, the Watchmen movie was released and underperformed. Everybody kind of took a step back and said, "Well, maybe the time's not right for an R-rated superhero movie, so put it on the shelf."

Watchmen has been a divisive film for fans, with some loving it and some hating it, but for a studio considering the bottom line, it definitely underperformed at the box office, making only $107 million in its domestic theatrical run. So it's only natural that the studio was scared off from an R-rated superhero movie, but with the success of Deadpool and other edgy superhero movies, the time is ripe to make an R-rated Killing Joke adaptation.

Then, the second time it went into production, the controversial material with Barbara Gordon and the Joker came into play:

A couple of years later, it came up again and we even had started production with character designs and stuff. But then that horrible shooting at the Dark Knight Rises theater happened and everybody got nervous again about it, because of gun violence, so we put it back on the shelf.

Barbara Gordon's fate in The Killing Joke is still the most controversial aspect of the graphic novel, and one of the biggest controversies in DC Comics in general. And according to Timm, that's still a major concern:

Go forward a couple of more years and it came up again. At this point we kind of looked at the whole thing and felt if we were going to do it, there were certain things about the original story that had always kind of bothered me. I mean the idea of adapting this story always kind of terrified me, because of how relentlessly grim and bleak it is. And what happens to Barbara Gordon in the story is very controversial to this day.

Luckily, it looks like the adaptation will have a more feminist take on things, as they are adding a 15-minute prologue that centers entirely on Barbara Gordon's character. Star Mark Hamill confirmed in the same interview that most of the new material involves Barbara, which will hopefully make her more well-rounded in the story:

If we just adapted The Killing Joke as an animated film, it would maybe be fifty-five minutes. They've actually done a really incredible job of supplementing it with Barbara Gordon/Batgirl material.

Batman: The Killing Joke will debut at San Diego Comic Con in July, and then will be released on Blu-ray on August 2.